Recently, there was a flurry of malicious short URls flying around which led to sites which then attempted to hijack your browser, install nasty scripts, codecs etc etc.
Most of the shortening sites now have a Preview feature, and it is worth enabling it, or using it, for peace of mind.
Bit.ly have a Firefox extension for previews which takes a moment to install
Tinyurl.com – just click to enable previews from tinyurl (requires cookies)
Tiny.cc did have preview pages but they currently seem to be disabled.
Does anyone know of any others we should add to the list?
Remember to offer a link that does allow a preview when using shortened URLs, your visitors like to know you are thinking about their security! And many people will not click on a link without knowing in advance where they will end up.